The need to detect and analyze transient events arises in many different contexts. One example involves underwater detection of acoustic signal sources. The electrical output of a conventional acoustic transducer (e.g., a microphone), includes many random noise components and perhaps some coherent background components as well (e.g., generated by water wave motions, etc.). Superimposed on such continuous "noise" components are relatively transient "signal" components associated with, for example, an incoming torpedo or a passing enemy submarine. The ability to quickly, accurately and reliably detect such superimposed transient "signal" components has long been sought after for useful application in many diverse situations.
Other situations or environments where reliable detection of such transient "signals" is desired may include security systems such as intrusion detection systems. These could be applicable to a home or a commercial setting. A transient signal which might contain desirable information could be the breaking of a window, while coherent background noise which it would be desirable to mask might include the operation of a refrigerator or other appliance. The present invention would be able to distinguish the transient episodes containing information from the "noise" sources such as the above-described refrigerator.
The present invention is particularly useful in the environment of security systems inasmuch as it reliably detects transient episodes in a manner so as to dramatically reduce false alarm rates which may be expected with other detector systems. Reliably reducing false alarm rates greatly reduces time and energy resource expenditures in monitoring the system.
Security systems may generally test for a variety of conditions such as smoke, water, fire or undesirable entry. All such sensors (or any other variety of sensors) could be utilized in accordance with the present invention either individually or in any combination.
Seismology detectors are concerned with another environment in which the present invention may be practiced with advantage. Seismology determinations may frequently require passive sensors which produce large quantities of data. The present invention rapidly and efficiently handles mass quantities of data by adaptively eliminating that data which is of less informational value. The detector apparatus and method of the present invention actually permits omission of large quantities of data (in terms of full term processing thereof), and accordingly permits rapid and efficient handling of large quantities of data.
A specific seismology application for the present invention could include a detector which considered nuclear or atomic detonations to be desirable transient episode information while earthquakes are considered undesirable background "noise" which should be filtered from the primary informational signals. The present invention would, in this particular environment, then detect nuclear detonations while masking all other information, i.e. treating all other signals as "noise".
I have now discovered a transient signal detection method and apparatus which I believe to be an improvement over any known prior detection technique and apparatus.
The methodology of the present invention is concerned with detecting transient events occurring in a sequence of input digital electrical signals by digitally scanning and processing the sequence of input digital signals to detect the occurrence of peak values within the digital signals, storing peak data which represents time of detected peak value occurrences and the magnitude of those detected occurrences, digitally analyzing time-consecutive patterns of the stored peak data to detect predefined patterns of peak values and storing corresponding peak-pattern data, and digitally analyzing the stored peak-pattern data to thereby detect the occurrence of transient events or episodes.
Detection or determination of signals based on detected-peak values is known. The mathematician and scientist Rice wrote in Selected Papers on Noise and Stochastic Processes (edited by Nelson Wax, copyright 1954, Dover Publications, New York) that signals may be determined by evaluating data measurements to determine peaks which occur therein.
The present invention is fundamentally different from the theoretical work of Rice inasmuch as no parametric assumptions are made by the apparatus and methods of the present invention. The theoretical work of Rice was always based on a Gaussian distribution of data. Real world applications present data patterns which are not of a Gaussian distribution. The adaptive feature of the present invention permits it to be an effective real-time filter and transient episode detector for any type of data, including non-Gaussian distributions.
Furthermore, the present invention is specifically concerned with digital apparatus which was not considered by Rice in his theoretical approach to looking at peak values. Accordingly, the present invention includes digital apparatus which makes no assumptions concerning a stream of input data, and reliably and efficiently provides detection of transient episodes contained within the stream of data by functioning as an adaptive filter thereon. The present invention not only determines peak values of a sequence of input digital signals, but it also digitally analyzes time-consecutive patterns of such peak data and then analyzes such peak patterns to detect and characterize transient episodes.